Method and apparatus for intercept of wireline communications

ABSTRACT

Method and apparatus for conducting surveillance in a SS7 Intelligent Network (IN) or Advanced Intelligent Network (AIN) provides in the case of AIN that an Info Analyzed trigger is armed in an end office switch and notifies a delivery function when a call is processed. The delivery function instructs the end office switch to forward the call to the delivery function, where it is accessed for monitoring forwarded back to the end office switch. A similar method is used to process calls received by the SUS. In the case of IN, the identity of a line card assigned to a subscriber under surveillance (SUS) is changed to a number dedicated to surveillance subjects. Calls originated by the SUS are forwarded to a delivery function, which identifies the SUS based on the dedicated number of the calling party, intercepts call content, and forwards the call back to the end office switch with the called party id aid the original number and id of the SUS. The end office switch then completes the call. A similar method is used to process calls received by the SUS.

This application is a continuation of U.S. non-provisional patentapplication No. 09/186,970, filed Nov. 5, 1998 now U.S. Pat No.6,549,613, Method and Apparatus for Interception of WirelineCommunications.

TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to telecommunications, and moreparticularly to the lawful intercept of telephony communications in atelecommunications network using Signaling System 7 (SS7).

BACKGROUND OF THE INVENTION

Court authorized access to telephone communications and call-identifyinginformation is one of the most crucial tools for effective lawenforcement. The introduction of new digitally based technologies,transmission modes, services, and features have made it increasinglydifficult for law enforcement to conduct court authorized electronicsurveillance. In October of 1994, at the request of the nation's lawenforcement community, Congress took action to protect public safety andnational security by enacting the Communications Assistance for LawEnforcement Act (CALEA). CALEA sets forth the interception assistancecapability requirements that telecommunications carriers need to meetand maintain within their networks to assist law enforcement inconducting electronic surveillance. These requirements apply to theintercept of wireline and wireless communications.

In order to meet the requirements of law enforcement to interceptcommunications, the telecommunications industry has defined an interfacespecification between a Telecommunication Service Provider (TSP) and aLaw Enforcement Agency (LEA), called the J-STD-025 (Lawfully AuthorizedElectronic Surveillance). The J-STD-025, “Lawfully Authorized ElectronicSurveillance”, is a joint standard by the Telecommunications IndustryAssociation (TIA) Committee TR45.2 and the Alliance forTelecommunications Industry Solutions (ATIS) CommitteeT1-Telecommunications. Compliance to J-STD-025 is seen by thetelecommunications industry as “safe harbor” under Section 107 of theCALEA, Public Law 103-414.

J-STD-025 views the intercept function as five broad categories: access,delivery, collection, service provider administration, and lawenforcement administration. The relationships between these functionalcategories are shown in FIG. 1. As illustrated in FIG. 1, the ServiceProvider Administrative Function 10 is responsible for controlling theTSP access and delivery functions. The Law Enforcement AdministrativeFunction 11 is responsible for controlling the LEA collection functions.The access function 14, consisting of one or more Intercept AccessPoints (IAPs), isolates an intercept subject's communications orcall-identifying information unobtrusively. The access function 14provides access to communications traversing a telecommunicationsnetwork. The deliver function 16 is responsible for acceptinginformation from one or more access functions 14 and deliveringintercepted communications to one or more collection functions 18. Thedelivery function 16 delivers information over two distinct types ofchannels: Call Content Channels (CCCs) and Call Data Channels (CDCs).The CCCs are generally used to transport call content, such as voice ordata communications. The CDCs are generally used to transport messageswhich report call-identifying information, such as calling partyidentities and called party identities. The collection function 18 isresponsible for collecting and analyzing intercepted communications andcall-identifying information. The collection function 18 is theresponsibility of the LEA.

SUMMARY OF THE INVENTION

The present invention provides method and apparatus for interceptingcalls for a subject under surveillance (SUS) in a Signaling System 7(SS7) compliant telephone system, or a telephone system with equivalentrelevant functions, by forwarding calls for a SUS from the end officeswitch to a delivery function, which in turn forwards the calls back tothe end office switch for further processing, and in addition obtainscall content and information as the call passes through the deliveryfunction. The delivery function can in turn deliver call content andinformation to a collection function.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a conceptualization of the electronic surveillancemodel of the Communications Assistance for Law Enforcement Act (CALEA).

FIG. 2 illustrates a first embodiment of the invention for use in a SS7network including AIN capability.

FIGS. 3–6 are call processing diagrams illustrating the operation of theembodiment of FIG. 2, using SS7 nomenclature.

FIG. 7 illustrates a first embodiment of the invention for use in a SS7network including IN capability only.

FIGS. 8–11 are call processing diagrams illustrating the operation ofthe embodiment of FIG. 7, using SS7 nomenclature.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description of the invention, reference ismade to the accompanying drawings which form a part thereof, and inwhich is shown, by way of illustration, specific embodiments in whichthe invention may be practiced. In the drawings, like numerals describesubstantially similar components throughout the several views. Theseembodiments are described in sufficient detail to enable those skilledin the art to practice the invention. Other embodiments may be utilizedand structural, logical, and electrical changes may be made withoutdeparting from the scope of the present invention. The followingdetailed description is, therefore, not to be taken in a limiting sense,and the scope of the present invention is defined only by the appendedclaims, along with the full scope of equivalents to which such claimsare entitled.

As described below, the present invention provides a network based CALEAsolution that does not require the modification of each and everyend-office switch. Instead, this solution operates in conjunction withthe Signaling System 7 (SS7) network, which today provides inter-switchcall set-up for approximately 90% of the access lines in the UnitedStates. The network based solution of the present invention do notrequire that a switch manufacturer make internal switch software orhardware modifications in order for the end-office switch utilized by acarrier to provide the capability requirements of CALEA. Instead,carriers choosing to employ a network-based solution make only minorconfiguration changes to individual switches. These limited changes areexpected to be easy for a carrier to implement and are consistent withnormal carrier modifications, such as changes to switch translations. Nodevelopment work on the part of a switch manufacturer should benecessary for the switch itself when the network-based solution of thepresent invention are used.

AIN Embodiment

Referring to FIG. 2, there is illustrated the architecture 10, of anexample embodiment of a network-based CALEA solution using (AdvancedIntelligent Network), according to the present invention. In thissolution, delivery function (DF) 20 contains a Service Control Point(DF-SCP) 22 and a Service Node (DF-SN) 24. The DF-SCP 22 is a TCAPapplication which responds to the AIN messages sent by the end-officeswitch 12. The DF-SN 24 is a switch which receives ISUP calls from theend-office switch 12 and sends those ISUP calls back to the sameend-office switch 12. In the meantime, the DF-SN 24 also duplicates thecall content and call identifying information to be sent to thecollection functions 30 at the law enforcement site. In this solution,the DF-SCP 22 and DF-SN 24 work together in receiving theincoming/outgoing calls to/from the target subscriber to be interceptedand delivering the call identifying information and call content to thelaw enforcement agency as defined in the J-STD-025. Using the AINtriggers in the end-office switch 12, the SCP interrupts the callprocessing in the end-office switch 12 and causes the end-office switch12 to send the call to the delivery function 20 instead of deliveringthe call to its real destination. The DF-SN 24 is responsible forreceiving the calls from the end-office switch 12 and sending the callsback to the same end-office switch 12. While doing that, it alsointercepts the call content together with the call identifyinginformation and delivers it to the law enforcement agency collectionfunctions 30 over call content (CCCs) and call data channels (CDCs), incompliance with J-STD-025.

The AIN interface between the end-office switch 12 and the deliveryfunction 20 is an SS7 interface using the Transaction CapabilitiesApplication Part (TCAP) layer. This interface carries only SS7signaling. On the other hand, the Integrated Services Digital NetworkUser Part (ISUP) interface between the end-office switch 12 and thedelivery function 20 is a T1 interface which may carry both SS7-ISUPsignaling and the call content (i.e., voice, modem data, etc.). It isalso possible that the SS7 signaling is routed through a SignalingTransfer Point (STP), and the T1 interface carries only the call contentchannels. At least one DS0 in the T1 interface per subject is requiredfor the call content (i.e., voice, modem data, etc.).

The J-STD-025 interface between the delivery function 20 and thecollection function(s) 34 is, in one example embodiment, two differentinterfaces: TCP/IP for call data and T1 for call content. The J-STD-025interface makes use of TCP/IP network to send the call identifyinginformation using the Lawfully Authorized Electronic SurveillanceProtocol (LAESP) messages as defined in J-STD-025. The call content(i.e., voice) maybe sent to the collection function(s) 30 using the T1interface. At least one DS0 per subject is required for the call content(i.e., voice) in this interface.

Referring now to FIGS. 2–5, a call processing sequence according to oneexample embodiment of the invention is described in more detail. Toinitialize intercept operation, InfoCollected and InfoAnalyzed AINtriggers are armed in the end-office switch 12 for the subscribers whichare under lawfully authorized electronic surveillance. The InfoCollectedtrigger is armed such that it shall be hit when the subject undersurveillance (SUS) originates a call. The InfoAnalyzed trigger is armedsuch that it shall be hit when the SUS receives a call from the publicswitched telephone network (PSTN). Whenever these triggers are hit, theService Switching Point (SSP) in the end-office switch 12 sends amessage to the DF-SCP 22 and waits for instructions from the DF-SCP 22about how to continue.

Calls Originated by the Subject Under Surveillance

When the SUS originates a call (40 a) on a subscriber line 16, theend-office switch 12 collects the digits dialed by the subject. Asillustrated in FIG. 3, upon collecting the digits, it will hit theInfoCollected trigger and send an InfoCollected AIN message (40 b) tothe delivery function 20. The DF-SCP 22 will receive this message, andinstruct the SSP of the end-office switch 25 to route the call to thedelivery function 20 using an AnalyzeRoute message (40 c). Uponreceiving the AnalyzeRoute message, the end-office switch 12 shall routethe call using ISUP (switch to switch circuit related messaging in SS7)signaling (Initial Address Message—IAM) to the delivery function 20 (40d). The DF-SN 24 will receive the incoming call sent by the end-officeswitch 12 using the ISUP trunks between the end-office and deliveryfunction 20. The delivery function 20 shall send an “Origination”message as defined in the J-STD-025 to the law enforcement agency toinform them about the call origination (40 e). This message shallinclude the target identity (calling party identity) and dialed digits(called party identity). The DF-SN 24, at the same time, shall send thesame call back to the end-office switch 12 using the ISUP trunks betweenthe end-office and delivery function 20 with the same calling and calledparty id (40 f). The end-office switch 12 shall route this call to itsdestination (41). As part of this sequence, the DF-SN 24 notifies thecollection function 30 with a CCOpen message (41 a) (pursuant toJ-STD-025) that the call content channel is opened after it receives theAddress Complete Message (ACM) from the end-office switch 12. It isafter this point that the DF-SN 24 starts duplicating the call content,and sends the call content to the collection function(s). Thus, the lawenforcement can hear the call progress tones, such as ring back, busy,fast busy, etc. As part of this sequence, the DF-SN 24 notifies thecollection function 30 with an Answer message (41 b) (pursuant toJ-STD-025) that the called party answered the incoming call after itreceives the Answer Message (ANM) from the end-office switch 12.

Calls Received by the Subject Under Surveillance

As illustrated in FIG. 4, when the subject under surveillance receives acall, the end-office switch 12 shall receive the call from anotherentity in the network (i.e., another line in the switch if it is localcall, or another switch in the network if it is an inter-office call, orinter-exchange carrier if it is a long distance call) (50 a). Uponreceiving this incoming call, the switch 12 shall realize that theInfoAnalyzed trigger is armed for the called party number SUS and hitthis trigger. Upon hitting this trigger, the end-office switch 12 shallsend an InfoAnalyzed AIN message to the delivery function 20 (50 b). TheDF-SCP 22 will receive this message, and instruct the end-office switch12 using an AnalyzeRoute message (50 c) to route the call to thedelivery function 20. Upon receiving the AnalyzeRoute message, theend-office switch 12 shall route the call using ISUP signaling to thedelivery function 20 (50 d). The DF-SN 24 will receive the incoming callsent by the end-office switch from the ISUP trunks between theend-office and delivery function 20. The delivery function 20 shall senda “Termination Attempt” message as defined in the J-STD-025 to the lawenforcement agency to inform them about the call delivery attempt (50e). This message shall include the target identity (called partyidentity) and calling party number (calling party identity). The DF-SN24, at the same time, shall send this call back to the same end-officeswitch 12 using the ISUP trunks between the end-office and deliveryfunction 20 with the same calling and called party id (50 f). Theend-office switch 12 shall hit the same trigger and send the sameInfoAnalyzed message (50 g) to the delivery function 20 once again. Butthis time, knowing that the call is already going through the deliveryfunction 20, the DF-SCP 24 shall send a Continue message to theend-office 12 instructing the SSP to deliver the call to its originaldestination (50 h). The end-office switch 12 shall route this call toits destination (51). As part of this sequence, the DF-SN 24 notifiesthe collection function 30 with a CCOpen message (41 a) (pursuant toJ-STD-025) that the call content channel is opened after it receives theAddress Complete Message (ACM) from the end-office switch 12. It isafter this point that the DF-SN 24 starts duplicating the call content,and sends the call content to the collection function(s). Thus, the lawenforcement can hear the call progress tones, such as ring back, busy,fast busy, etc. As part of this sequence, the DF-SN 24 notifies thecollection function 30 with an Answer message (41 b) (pursuant toJ-STD-025) that the SUS answered the incoming call after it receives theAnswer Message (ANM) from the end-office switch 12.

In this architecture, the call is always going through the deliveryfunction 20 like a tandem switch; therefore, the call release is donethe same way it is performed in any regular ISUP call as illustrated inFIGS. 5 and 6. After the call is released (60) with the Release (REL)Messages, the delivery function 20 shall notify the law enforcementagency about the release of the call using a “Release” message asdefined in the J-STD-025, and clear its resources (61), and the switch12 completes the call release sequence with Release Complete (RLC)Messages (62).

It is noted that the InfoAnalyzed trigger can also be used for forwardedcalls since it is still the same subscriber that has that trigger armed.The call waiting feature is also supported. When the subscriber is busyand a second call comes in, the second call is still routed through thedelivery function 20. The O_Mid_Call and T_Mid_Call triggers need to bearmed for the SUS with the call waiting feature to get the hook flashindications to the delivery function 20 to be able to determine that thesubscriber is switching between two parties using the call waitingfeature. The delivery function 20 shall generate the “Change” message asdefined in the J-STD-025 and send it the collection function(s) 30.

The three-way calling feature is also supported by the above-describedembodiment. When the SUS originates a second call when he/she is alreadyengaged in a call using the hook flash and the three-way callingfeature, the second call is still routed through the delivery function20. The O_Mid_Call and T_Mid_Call triggers need to be armed for the SUSwith the three-way calling feature to get the hook flash indications tothe delivery function 20 to be able to determine that the subscriber isswitching between two parties using the three-way calling feature. Thedelivery function 20 can also generate the “Change” message as definedin the J-STD-025 and send it the collection function(s) 30. It is notedthat there may be some modifications required depending on theimplementation of the three-way calling feature in a particular specificend-office switch 12, since there may be some interaction with the callwaiting feature. Also, the delivery function 20 software may need to becustomized for different implementations of the switch.

IN Embodiment

Referring now to FIG. 7, there is illustrated an embodiment 70 of theinvention used in a Intellegent Network (IN) telephony system. In thissolution, the delivery function 80 contains only a Service Node (DF-SN)82. The DF-SN 82 of the delivery function 80 is a switch which receivesISUP calls from the end-office switch 72 and sends those ISUP calls backto the same end-office switch 72. While doing that, it will alsointercept the call content and duplicate them, and then deliver the callcontent together with the call identifying information to the lawenforcement agency over call content and call data channels. In thissolution, the end-office switch 72 needs to be configured andintelligent enough to send the calls originated/received by the subjectunder surveillance to the delivery function 80 over the ISUP interfacebetween them. Therefore, this solution relies on the intelligence andconfigurability of the end-office switch 72.

The ISUP interface between the end-office switch 72 and the deliveryfunction 80 is a T1 interface which may carry both SS7-ISUP signalingand the call content (i.e., voice, modem data, etc.). It is alsopossible that the SS7 signaling is routed through a Signaling TransferPoint (STP), and the T1 interface carries only the call contentchannels. At least one DS0 in the T1 interface per subject is requiredfor the call content (i.e., voice, modem data, etc.). The J-STD-025interface between the delivery function 80 and the collectionfunction(s) 90 is the same as described above with respect toarchitecture 10.

In order to implement embodiment 70, there must be available some extraNXX-XXXX numbers in the switch 72 for the surveillance. Also, some ofthe NXX-XXXX numbers have to be routable to the delivery function 80 viaISUP trunks. The end-office switch 72 also needs to be configured suchthat a call can be routed based on the calling party number 72. Further,it is required that the end-office operator can change the line identityof the line card dedicated to the SUS's.

The embodiment 70 is best described using an example. Assume for thisdescription that the subject under surveillance (SUS) has the phonenumber 203-925-6100 and that the number 203-925-9999 is reserved in theend-office switch 72 for lawfully authorized electronic surveillance.The routing table of the switch should thus be configured such that whena call is originated from the 203-925-9999 number, the call is routed tothe delivery function 80. When a law enforcement agency comes with acourt order for the SUS, the end-office operator shall change theidentity of the line card dedicated for SUS to 203-925-9999 from203-925-6100. The operator also needs to change the routing tables ofthe switch 72 such that when a call comes in to the number 203-925-6100,the call will be routed to the delivery function 80 via the ISUP trunksgoing to the delivery function 80.

Calls Originated by the Subject Under Surveillance

The following description is made with respect to FIG. 8. When the SUSoriginates a call (100 a) by dialing, for example, 203-925-5555, theend-office switch 72 shall send the call to the delivery function 80 viathe ISUP trunks between the end-office switch 72 and the deliveryfunction 80 (100 b). The calling party address in the IAM message shallbe 203-925-9999, and the called party address shall be the 203-925-5555.The delivery function 80 shall receive this call and send the call backto the end-office switch 72 again using the ISUP trunks between theend-office switch 72 and the delivery function 80 (100 c). This time thecalling party address in the IAM message shall be 203-925-6100, and thecalled party address shall be the 203-925-5555. The end-office switch 72shall route this call just like it does to any other call (101). Sincethe call goes through the delivery function 80, delivery function 80shall duplicate the call content and deliver the call data and callcontent to the law enforcement site(s). As part of this sequence, theDF-SN 82 notifies the collection function 90 with a CCOpen message (101)(pursuant to J-STD-025) that the call content channel is opened after itreceives the Address Complete Message (ACM) from the end-office switch72. It is after this point that the DF-SN 82 starts duplicating the callcontent, and sends the call content to the collection function(s). Thus,the law enforcement can hear the call progress tones, such as ring back,busy, fast busy, etc. As part of this sequence, the DF-SN 82 notifiesthe collection function 90 with an Answer message (101) (pursuant toJ-STD-025) that the called party answered the incoming call after itreceives the Answer Message (ANM) from the end-office switch 72.

Calls Received by the Subject Under Surveillance

The following description is made with respect to FIG. 9. When the SUSreceives a call (102 a), for example, from 203-925-5555, the end-officeswitch 72 shall send the call to the delivery function 80 via the ISUPtrunks between the end-office switch 72 and the delivery function 80(102 b). The calling party address in the IAM message shall be203-925-5555, and the called party address shall be the 203-925-6100.The delivery function 80 shall receive this call and send the call backto the end-office switch 72 again using the ISUP trunks between theend-office switch 72 and the delivery function 80 (102 c). The callingparty address in the IAM message shall still be 203-925-5555, but thecalled party address will be set to 203-925-9999 by the deliveryfunction 80. The end-office switch 72 shall deliver this call to the SUSjust like it does to any other call. Since the call goes through thedelivery function 80, the delivery function 80 shall duplicate the callcontent and deliver the call data and call content to the lawenforcement site(s). As part of this sequence, the DF-SN 82 notifies thecollection function 90 with a CCOpen message (103) (pursuant toJ-STD-025) that the call content channel is opened after it receives theAddress Complete Message (ACM) from the end-office switch 72. It isafter this point that the DF-SN 82 starts duplicating the call content,and sends the call content to the collection function(s). Thus, the lawenforcement can hear the call progress tones, such as ring back, busy,fast busy, etc. As part of this sequence, the DF-SN 82 notifies thecollection function 90 with an Answer message (103) (pursuant toJ-STD-025) that the SUS answered the incoming call after it receives theAnswer Message (ANM) from the end-office switch 72.

In this architecture, the call is always going through the deliveryfunction 80 like a tandem switch; therefore, the call release is donethe same way it is performed in any regular ISUP call. After the call isreleased, the delivery function 80 shall notify the law enforcementagency about the release of the call (104) using a “Release” message asdefined in the J-STD-025, and clear its resources (105). These releasesequences are illustrated in FIGS. 10 and 11.

Call forwarding feature is also reported by this implementation. Sincethe subject's phone number is moved to the delivery function 80, all thecalls coming to the subject will still go through the delivery function80 regardless of the call forwarding. However, it is noted that if thesubject under surveillance can activate/deactivate its call forwardingfeature by dialing the *FC, the delivery function 80 will not be awareof those changes after the surveillance is started. In these cases, thedelivery function will inform the operator by generating alarms, andoperator will make the changes in the subscriber profile within theend-office switch.

The call waiting feature is supported in this embodiment as follows.When the subscriber is busy and a second call comes in, the second callis still routed through the delivery function 80. When the second callcomes in, and the SUS answers the call by hook flash, the deliveryfunction 80 receives an ANM message and will notify the law enforcementusing the “Change” message as defined in the J-STD-025, and also sendthe call content using a separate channel.

The three-way calling embodiment is supported in this embodiment asfollows. When the subscriber originates a second call when he/she isalready engaged in a call, using the hook flash and the three-waycalling feature, the second call is still routed through the deliveryfunction 80. When the second call is answered by the called party, thedelivery function 80 receives an ANM message and will notify the lawenforcement using the “Change” message as defined in the J-STD-025, andalso send the call content using a separate channel.

Implementations Features

The delivery function in the embodiments described above can beimplemented in either hardware or software or a combination thereof.Likewise, many of the functions or devices described above asimplemented in hardware or software are equally implementable in wholeor in part in software or hardware, respectively. Thus, with respect tothe claims appended hereto, the term “unit” shall mean an electronicentity, which may be, for example, a hardware circuit or device orsoftware executing on a computing platform, or a combination of such.

As an alternate implementation, the delivery function can also accessthe SS7-ISUP signaling information using a passive monitoring devicethat can listen to the SS7 links and filter those messages that arerelated to the SUS. The delivery function will then generate theJ-STD-025 messages from the information gathered by the passivemonitoring device.

It shall be further noted that the invention is in no way limited toapplication to SS7 AIN or IN networks. Rather, the invention will workin connection with any telephone network which includes substantiallythe same functionality, or at least portions thereof, of an SS7 AIN orIN network that is relevant to the implementation of the invention.Moreover, the invention could be applied to any telephone network thatcan be customized to include the capabilities needed to forward calls tothe delivery function as described herein.

Conclusion

Thus, the invention as described above provides methods for allprocessing and apparatus for example, carrying out the methods, in orderto provide electronic surveillance in a SS7 Intelligent Network (IN) orAdvanced Intelligent Network (AIN). As noted above, one potentialadvantage of this methodology and apparatus is that it can beimplemented with a minimal number of modifications to the existing endoffice equipment.

1. A method of intercepting calls for a subject under surveillance (SUS)in a Signaling System 7 (SS7) Intelligent Network (IN) complianttelephone system, wherein the SUS has an assigned first telephone numberthat others use to call the SUS on a SUS subscriber line, the methodcomprising: assigning to the SUS a surveillance telephone number forsurveillance purposes, wherein both the first telephone number and theassigned surveillance telephone number are used to route telephone callsto the SUS, and wherein the surveillance telephone number and the firsttelephone number for the SUS are different; in an end office switch,configuring the identity of a line card for the SUS to the surveillancetelephone number so that calls placed by the SUS identify the SUS as acalling party by the surveillance telephone number; configuring arouting table of the end office switch so that the calls placed by theSUS to a called party telephone number are forwarded to a deliveryfunction unit, and so that calls placed to the SUS using the firsttelephone number are forwarded to the delivery function unit; thedelivery function unit receiving the forwarded calls, and identifyingthe SUS by the surveillance telephone number as the calling party or bythe first telephone number as a called party; the delivery function unitforwarding calls placed by the SUS back to the end office switch withthe calling party identified with the SUS's first telephone number andwith the called party telephone number provided by the SUS so that theend office switch forwards calls placed by the SUS to the called party,and forwarding calls placed to the SUS to the end office switch with thesurveillance telephone number as the called party telephone number andwith the calling party telephone number the same as received from theend office switch so that calls placed to the SUS are connected to theSUS's subscriber line; and the delivery function unit further obtaininga copy of call content for any calls forwarded through the deliveryfunction unit.
 2. A method according to claim 1 wherein the deliveryfunction unit sends the call content to a remote location according toone or more court orders pertinent to the SUS.
 3. A method according toclaim 2 wherein the remote location includes a collection function forcollecting the call content.
 4. A method according to claim 1 including:routing to the delivery function unit a second call to the SUS'ssubscriber line using a call waiting feature of the end office switch;and the delivery function unit generating a change message when the SUSswitches between the first and second calls.
 5. A method according toclaim 1 including: routing to the delivery function unit a second calloriginated on the SUS's subscriber line using a three way callingfeature of the end office switch; and the delivery function unitgenerating a change message when the SUS switches between the first andsecond calls.
 6. A method according to claim 1 wherein a call to a SUS'ssubscriber line is forwarded by the end office switch using a callforward feature.
 7. A delivery function apparatus for use with a SS7Intelligent Network (IN) compliant telephone system, comprising a SS7 INcompatible call processing unit configured to receive a first forwardedSS7 call, wherein identifying information for the first forwarded callindicates that the first forwarded call was placed by a suspect undersurveillance (SUS), and configured to output the first forwarded callwith a calling party telephone number equal to a telephone numberprovided to the SUS; the call processing unit further configured toreceive a second forwarded SS7 call, wherein identifying information forthe second forwarded call indicates that a called party is the SUS, andconfigured to output the second forwarded call with a called partytelephone number equal to a telephone number of the SUS's telephoneline, so that the forwarded call is connected to the SUS; wherein thecalled party telephone number output with the second forwarded call is asurveillance telephone number that is different from the calling partytelephone number output with the first forwarded call; the callprocessing unit further configured to output call content to acollection function.
 8. A method of intercepting calls for a subjectunder surveillance (SUS) having a telephone line in a Signaling System 7(SS7) Intelligent Network (IN) compliant telephone system, wherein theSUS has an assigned first telephone number that others use to call theSUS on the SUS's telephone line, the method comprising: assigning to theSUS a surveillance telephone number for surveillance purposes, whereinboth the first telephone number and the assigned surveillance telephonenumber are used to route telephone calls to the SUS, and wherein thesurveillance telephone number and the first telephone number for the SUSare different; in an end office switch, configuring the identity of aline card for the SUS to the surveillance telephone number so that callsplaced by the SUS to a called party identify the SUS as a calling partyby the surveillance telephone number; configuring a routing table of theend office switch so that the calls placed by the SUS are forwarded to adelivery function unit; the delivery function unit receiving theforwarded calls, and identifying the SUS by the surveillance telephonenumber as the calling party or by the first telephone number as thecalled party; the delivery function unit forwarding calls placed by theSUS back to the end office switch with the calling party identified withthe SUS's first telephone number and with the called party telephonenumber provided by the SUS so that the end office switch forwards thecall to the called party; and the delivery function unit furtherobtaining a copy of call content for calls forwarded through thedelivery function unit.